Optical waveguide structures fabricated in planar forms can perform a variety of functions in optical light-paths. These include optical coupling in various configurations, such as multi-channel star arrays, and multiplexing or demultiplexing through phasar or grating devices. Such waveguides also hold the promise of being lower in cost than discrete optical devices which are fabricated from fiber and micro-optic components. In the future, they may provide a platform for hybrid, electro-optic devices.
For each signal to be processed, the optical waveguide must be connected to an optical fiber carrying an input signal, and to a second optical fiber carrying the processed signal. Traditionally, these connections, commonly referred to as "pigtails," have been accomplished with organic adhesives, such as methacrylate or epoxy adhesives. These polymeric adhesives offer simple fabrication, fair index matching, and good bonding characteristics.
However, they are hydratively unstable. This limits their usefulness in wet environments such as are encountered in underwater and high humidity applications. It has also been reported that many of these adhesives have questionable stability when subjected to environmental extremes in temperature and pressure.
Even a slight deterioration in the optical properties of the adhesive will seriously impair transmission of optical signals through the fiber-waveguide network. Thus, instability can have disastrous consequences, making the organic, or "soft," pigtail unsuitable for many applications.
The need for a stable, optical fiber-to-planar waveguide connection has led to a vitreous seal using a glass ftit as such, or admixed with a mill addition. The resulting joint is hydratively stable and relatively strong. However, it may involve stresses caused by differences in the coefficients of thermal expansion between the components; also a higher than desired sealing temperature.
The present invention is directed to overcoming these and other deficiencies in the art.